21221356121 has 16 divisors (see below), whose sum is σ = 24360424704. Its totient is φ = 18109238784.

The previous prime is 21221356103. The next prime is 21221356127. The reversal of 21221356121 is 12165312212.

It is not a de Polignac number, because 21221356121 - 2²² = 21217161817 is a prime.

It is a super-2 number, since 2×21221356121² (a number of 21 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21221356127) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4403105 + ... + 4407921.

It is an arithmetic number, because the mean of its divisors is an integer number (1522526544).

Almost surely, 2^21221356121 is an apocalyptic number.

It is an amenable number.

21221356121 is a deficient number, since it is larger than the sum of its proper divisors (3139068583).

21221356121 is a wasteful number, since it uses less digits than its factorization.

21221356121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7480.

The product of its digits is 1440, while the sum is 26.

Adding to 21221356121 its reverse (12165312212), we get a palindrome (33386668333).

The spelling of 21221356121 in words is "twenty-one billion, two hundred twenty-one million, three hundred fifty-six thousand, one hundred twenty-one".